1. Field of the Invention
The present invention relates to a valve arrangement for a vacuum pump and including a valve head displaceable substantially perpendicular to a flow direction of fluid through the valve arrangement, a valve seat, and a valve spring for biasing the valve head into an abutment engagement with the valve seat.
2. Description of the Prior Art
A valve arrangement of the type described above is used primarily in vacuum pumps which are characterized by a dry operation in the compression chamber. The vacuum pumps with a dry operation in the compression chamber necessitate use of lubricant-free components, e.g., valves which are directly connected with the pumps.
Generally, in valves used with the above described type of vacuum pumps, the closing elements which, as a rule, is called a valve head, is displaced in the flow direction. In the closed condition, the valve head flatly abuts a valve seat and is biased to its closing position by a spring. There exist different designs of valve springs used in valves for vacuum pumps with a dry operation in the compression chamber. One of such springs is disclosed in U.S. Pat. No. 4,790,726. However, all of the known design have serious drawbacks. With metallic springs contacting non-lubricated surfaces, which is the case in vacuum pumps with a dry operation in the compression chamber, the wear of the cooperating elements can lead to their malfunction.
It was also proposed to use, as a valve spring, a massive O-ring in valves for lubricant-free pumps. However, such an O-ring is characterized by a poor springing action. A primary reason of a poor springing action of an O-ring consists in that its material in the center of the ring can be deformed only with much difficulty, and a very large force needs to be applied to effect deformation. In addition, a deformable O-ring has a cross-section that is determined by two opposite surfaces associated with respective cylindrical halfshells. This results in a non-linear springing action and in a very small deformation range.
It was also proposed to use spring elements formed of metal but covered with an elastic jacket. Such spring elements are very expensive in production.
Accordingly, an object of the present invention is to provide a valve arrangement in which the above-discussed drawbacks of known valve springs are eliminated. Another object of the present invention is to provide a valve arrangement with such valve springs that would insure a varied application of the valve arrangement, in particular, for operation in vacuum.